Reduced size gravimetric blender

ABSTRACT

A gravimetric blender of a reduced size mounted to be directly over the feed trough of small molding machines or extruders. The blender has an upright hollow rectangular frame with a transparent panel. The top of the frame forms a cradle for removably supporting a plurality of hoppers having a bottom discharge controlled by a valve mechanism. The valve mechanism is mounted on each hopper and is connected to a control station having a quick-disconnect fitting on the hopper. The hoppers discharge sequentially into a weigh bin supported on a load cell connected to the control station of the blender. The weigh bin has an openable bottom portion pivotally mounted thereon for actuation by the control station when the appropriate weight is registered by the load cell. The weigh bin discharges into a mixing chamber having an agitator or mixer removably mounted therein. The mixer is journaled for rotation in the transparent panel which is removable so that when the panel is removed, the mixer agitator is disengaged from its drive and removed with the panel.

RELATED APPLICATION

The present application claims priority from provisional application No.60/045,343, filed on May 2, 1997, for a “Reduced Size GravimetricBlender”, which is incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to methods and apparatus for providingprecisely measured amounts of granular materials preparatory to furtherprocessing of the combined granular materials and specifically togravimetric blenders providing precisely measured amounts of plasticresin material and mixing these components prior to supplying theblended mixture to plastics manufacturing and processing equipment suchas plastic injection molding, compression molding and extrusionequipment.

FIELD OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART

The modern gravimetric blender was essentially originated by theapplicant of this invention and is widely used throughout the world byindustries concerned with precision feeding of granular material,especially plastic resin material.

Gravimetric blenders operate by blending solid plastic resin materialcomponents and additives, by weight, in batches.

Typically batches of material may consist of several solid materialcomponents. One of these may be “regrind”, consisting of ground plasticresin which had previously been molded or extruded and which eitherresulted in a defective product or was excess material not formed into adesired product.

Another component may be “natural” plastic resin which is virgin innature in the sense that it has not previously been processed into amolded or extruded plastic part.

Yet another component may be a solid color material, typically flakes orfreeze dried material, used to produce a desired color of the finishedplastic part.

Still yet another component may be an additive used to adjust the blendto provide required performance characteristics during molding,extrusion or subsequent processing.

The gravimetric blender as originated by the applicant and as copiedwidely throughout the world typically includes hoppers for each of thecomponents of the solid material to be blended together. Typicallyseveral hoppers or several compartments in a hopper may be provided,such as one compartment for “regrind” material, one compartment for“natural” material, one component for solid color additive material andone compartment for “additive”.

When the gravimetric blender operates, the unit desirably operatesautomatically, adding each of the component solid materials in theproper, desired percentages. Each solid material component is dispensedby weight into a single weigh bin. Once the proper amounts of eachcomponent have been serially dispensed into the weigh bin, all of thecomponents are dropped together into a mixing chamber from the weighbin.

Mixing is performed, preferably continuously, and preferably even asadditional batches component are dispensed in the mixing chamber. Whenmixing is complete, the resulting blend is preferably provided directlyto the desired molding or extrusion machine.

Feedback control of the dispensed amounts of each solid materialcomponent provided to the weigh bin and measured by weight assures thatin the event of an error in the amount of a dispensed component, thesucceeding batch may have the blend adjusted to account for the errordetected in the preceding batch of blended material.

As one of the components forming a part of the resulting blend it isknown to supply solid color additives to the blend in order to provide ablend of a desired color. These color additives may be flaked pigmentson wax carriers or in freeze dried form. It is also known to provide thecolor as pigment powder constituting one component of the resultingblend.

SUMMARY OF THE INVENTION

In one of its aspects this invention provides a gravimetric blenderincluding a frame, a material storage hopper removably mounted on theframe, valve means proximate the hopper bottom for dispensing materialwithin the hopper, and means connected to the hopper and remaining soupon removal of the hopper from the frame, for actuating the valve meansto downwardly dispense material within the hopper, a weigh bin connectedto the frame below the hopper, means connected to the frame for sensingweight of material in the bin, and a mix chamber below the weigh bin.

Desirably, the means for actuating the valve is fixedly connected to thehopper, the actuating means is at least partially within the hopper, thevalve means is at least partially within the hopper, the hopper ismanually removable from the frame, and it further includes a pluralityof hoppers, each with valve means therewithin and respective individualvalve actuation means. The actuating means is pneumatically driven andincludes a vertically elongated member for transmitting motion to thevalve.

The gravimetric blender includes a frame, a weigh bin, means connectedto the frame for sensing weight of material in the bin, a mix chamberbelow the bin and connected to the frame, means connected to the framefor selectably contacting and opening the bin to release material in thebin downwardly into the mix chamber. The blender further preferablyincludes means for biasing an openable portion of the bin towards aclosed position; the openable portion is preferably movable about apivot; the openable portion preferably pivots about a horizontal axis;the means for selectably contacting and opening the bin is preferablypneumatically actuated; the means for selectably contacting and openingthe bin is preferably a piston-cylinder combination; the cylinder ispreferably outward of the frame; the piston preferably movestransversely to the axis about which the openable portion pivots; thepiston may contact the bin directly or indirectly; the openable portionis preferably pivotally connected to a remaining, stationary portion ofthe bin.

The piston is preferably disconnected from the bin when the movableportion is at the closed position.

The invention further includes means for selectably contacting andopening the bin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation of a reduced size gravimetric blenderillustrating principally, but not entirely, design aspects theinvention.

FIG. 2 is a rear elevation of a reduced size gravimetric blenderillustrated in FIG. 1, illustrating principally, but not entirely,design aspects of the invention.

FIG. 3 is a left side (with reference to the blender positioned as shownin FIG. 1) elevation of a reduced size gravimetric blender illustratedin FIGS. 1 and 2, illustrating principally, but not entirely, designaspects of the invention.

FIG. 4 is a right side (with reference to the blender positioned asshown in FIG. 1) elevation of a reduced size gravimetric blenderillustrated in FIGS. 1, 2 and 3, illustrating principally, but notentirely, design aspects of the invention.

FIG. 5 is a bottom view of a reduced size gravimetric blenderillustrated in FIGS. 1, 2, 3 and 4, illustrating principally, but notentirely, design aspects of the invention.

FIG. 6 is a top elevation of a reduced size gravimetric blenderillustrated in FIGS. 1, 2, 3, 4 and 5, illustrating principally, but notentirely, design aspects of the invention.

FIG. 7 is a top elevation of a reduced size gravimetric blenderillustrated in FIGS. 1, 2, 3, 4, 5 and 6, but with the top of the hopperopen, illustrating principally, but not entirely, design aspects of theinvention.

FIG. 8 is a front elevation of a reduced size gravimetric blender shownin FIGS. 1 through 7, but with the hopper removed, illustratingprincipally, but not exclusively, design aspects of the invention.

FIG. 9 is a rear elevation of a reduced size gravimetric blender shownin FIGS. 1 through 8, but with the hopper removed, illustratingprincipally, but not exclusively, design aspects of the invention.

FIG. 10 is a left side elevation (with reference to the blenderpositioned as shown in FIG. 8) of a reduced size gravimetric blendershown in FIGS. 1 through 9, but with the hopper removed, illustratingprincipally, but not exclusively, design aspects of the invention.

FIG. 11 is a right side elevation of a reduced size gravimetric blendershown in FIGS. 1 through 10, but with the hopper removed, illustratingprincipally, but not exclusively, design aspects of the invention.

FIG. 12 is a top view of a reduced size gravimetric blender shown inFIGS. 1 through 11, but with the hopper removed, illustratingprincipally, but not exclusively, design aspects of the invention.

FIG. 13 is a front elevation of the reduced size gravimetric blenderillustrated in FIGS. 1 through 12, with the hoppers in place.

FIG. 14 is a top view of the reduced size gravimetric blenderillustrated in FIGS. 1 through 13, with the hoppers in place and thecover removed from the hoppers.

FIG. 15 is a top view of one of the hoppers of the reduced sizegravimetric blender illustrated in FIGS. 1 through 14 with the coverremoved.

FIG. 16 is a sectional view taken at arrows 16—16 in FIG. 15 of thehopper illustrated in FIG. 15 showing the valve and the hopper in anopen position.

FIG. 17 is a sectional view similar to FIG. 16 showing the valve and thehopper in a closed position.

FIG. 18 is a side elevation of a movable tubular portion of a valve forpulsing, controlled feeding operation which resides within a hopper suchas illustrated in FIGS. 15 through 17.

FIG. 19 is a front elevation of the structure illustrated in FIG. 18.

FIG. 20 is a top view of a valve holder base part used at the bottom ofa hopper such as illustrated in FIGS. 15, 16 and 17.

FIG. 21 is a front view of the valve holder base part illustrated inFIG. 20.

FIG. 22 is a side view of the valve holder base part illustrated in FIG.20.

FIG. 23 is a front elevation of a valve skirt which fits within a hoppersuch as illustrated in FIGS. 15 through 17.

FIG. 24 is a top view of the valve skirt illustrated in FIG. 23.

FIG. 25 is a side elevation of the valve skirt illustrated in FIGS. 23and 24.

FIG. 26 is a front elevation of a movable tubular portion of a valve foron-off, shut-off operation, which resides within a hopper such asillustrated in FIGS. 15 through 17.

FIG. 27 is a side view of the movable tubular portion illustrated inFIG. 26 of a valve which resides within a hopper such as illustrated inFIGS. 15 through 17.

FIG. 28 is a top view of the movable tubular portion illustrated inFIGS. 26 and 27 of a valve which resides within a hopper such asillustrated in FIGS. 15 through 17.

FIG. 29 is a front view of the female member of a coupling between thereciprocating rotating pneumatic drive and the agitator.

FIG. 30 is a side sectional view of the structure illustrated in FIG.29.

FIG. 31 is a side view of a male portion of the coupling apparatus forthe agitator and the pneumatic drive apparatus.

FIG. 32 is a front view of the structure illustrated in FIG. 31.

FIG. 33 is a front elevation of the agitator.

FIG. 34 is a side elevation of the agitator shown in FIG. 33.

FIG. 35 is a front view of the liner for the mix chamber.

FIG. 36 is a top view of the liner for the mix chamber illustrated inFIG. 35.

FIG. 37 is a front view of the weigh bin dump flap.

FIG. 38 is a side view of the weigh bin dump flap illustrated in FIG.37.

FIG. 39 is a front elevation of the stationary weigh bin basket portion.

FIG. 40 is a right side elevation of the structure illustrated in FIG.39.

DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST MODE KNOWN FORPRACTICING THE INVENTION

Referring to FIGS. 1-14 and to FIG. 13 in particular, a gravimetricblender is designated generally 10 and includes a hopper assembly 11including a plurality of hoppers, which are individually designatedgenerally 12. The collection of hoppers 12, each of which isindividually removable from blender 10 manually, without the use oftools, is supported by a frame designated generally 14 which holds aweigh bin 15 into which portions of solid plastic resin or othergranular or powdery material can be metered and weighed prior to releaseinto a mix chamber 20 as described below.

Frame 14 preferably includes four upstanding side panel members, threeof which are preferably steel and formed from a single sheet, bent toform the three sides, with each of the three sides being identified 30.The remaining front side panel of frame 14, which is removable anddetachable from sides 30, is designated 17 in the drawings and ispreferably clear, transparent plastic.

Hopper assembly 11 with the desirable plurality of hoppers 12 allows aplurality of different solid resinous materials to be dispensed from thehoppers 12 into weigh bin 15 by suitable valve mechanisms, designatedgenerally 19, located within and proximate to the bottom of a givenhopper 12. The hoppers 12 are individually manually mountable on andremovable from gravimetric blender 10 by hand, without use of tools.

The upper extremity of each solid side panel 30 of frame 14 is formedinto an outwardly flared guide flap 34. In the preferred configurationsince there are three solid side panels 30, three outwardly flared guideflaps 34 result. Outwardly flared guide flaps 34 are integral with andformed as a part of solid side panels 30 by bending the upperextremities of solid side panels into the shape illustrated in thedrawings, particularly in FIG. 13.

A fourth outwardly flared guide flap 34A is positioned above transparentremovable front panel 17 and is welded to the upper extremities of thetwo solid side panels 30 between which transparent removable front panel17 fits.

Outwardly flared guide flaps 34 preferably include tab members 36 whichare perpendicular to the remaining portion of guide flap 34 and extendtherefrom in a generally downwardly direction. This provides aconvenient hand-hold for an operator while lifting a hopper 12 fromblender 10.

Guide flaps 34 have vertical slots formed therein at the centralportions thereof with the slots extending from a lower extremity ofguide flap 34 upwardly but not to the juncture of the upper edge ofguide flap 34 with tab 36. These slots retain a cross-frame 21 whichconsists of two inter-engaging members. One of these members, whichextends parallel to transparent removable front panel 17, is indicatedas 21A in the figures; the other member is indicated as 21 in thefigures, particularly FIG. 13.

Cross-members 21, 21A have slots formed at the central portions thereof,with one member having an upwardly facing slot and the other memberhaving a downwardly facing slot for engagement one with another. Hence,when cross-members 21, 21A are resident in the vertical slots inoutwardly flared guide flaps 34, a cross-frame defined by cross-members21 is fixed in position relative to frame 14 for supporting hoppers 12in position.

Cross-members 21 are notched with the notches formed in the lowersurface thereof, to engage the unnumbered vertical slots in outwardlyflared guide flaps 34. Engagement of the notches in the lower portionsof cross-members 21 with these upwardly extending slots and the angularorientation of outwardly flared guide flaps 34 securely retains thecross-frame defined by cross-members 21 in place.

Hoppers 12 are easily individually manually lowered into position incross-frame 21 and are easily manually lifted out thereof.

As shown in FIGS. 15 through 17, gravimetric blender 10 further includespneumatically actuated spring-loaded piston means housed withincylinders which are wholly within hoppers 12. The piston-cylindercombinations, which are designated generally 18 in the drawings, areindirectly fixedly connected to hoppers 12 via skirts 38. Pistons of thepiston-cylinder combinations 18 are preferably spring-loaded and operatein response to pressurized air to actuate tubular valve members housedwithin skirts 38. When the pistons move the tubular valve members housedwithin skirts 38, in a direction indicated by arrow A in FIGS. 16 and17, a given piston moves a given associated valve member verticallydownwardly into the position illustrated in FIG. 16, discharginggranular material contained within the associated hopper 12 downwardlyinto the weigh bin of the blender.

When pneumatic pressure supplied to a given piston is released, aninternal spring portion of the piston-cylinder combination causes thepiston to retract, thereby retracting the valve member in a verticallyupward direction, into the position illustrated in FIG. 17, at which thevalve is closed and granular material cannot flow downwardly from hopper12 into the weigh bin 15.

The valve members are designated generally 19 in FIGS. 16 and 17. Eachvalve member includes a tubular, preferably cylindrically configuredstem member designated generally 40 and illustrated in FIGS. 26, 27 and28.

Tubular stem member 40 is connected to a movable piston portion ofpiston-cylinder combination 18 via a piston shaft 42 as illustrated inFIG. 16. Preferably, piston shaft 42 does not directly connect withtubular stem member 40 but rather has a yoke or clevis 44 connected tothe end of piston shaft 42 which is remote from piston-cylindercombination 18. Yoke 44 includes a pair of arms 46 extending from a bodyportion of yoke 44 in the manner illustrated in FIG. 16. Yoke arms 46are bored with the bores through parallel yoke arms 46 being transversethereto and parallel one with another.

A pin 48 connects yoke 44 with tubular stem member 40 by passing throughthe parallel bores in yoke arms 46 and through an aperture 50 in tubularstem member 40. Pin 48 fits slidably in aperture 50 and the bores inyoke arms 46.

Tubular stem member 40 is housed within a skirt designated generally 38in FIGS. 15 through 17 and illustrated in stand-alone form in FIGS. 23,24 and 25. Skirt 38 is of generally rectangular configuration, asillustrated in FIG. 23, and has two adjoining closed sides 52, 54 andtwo non-adjoining open sides 56, 58, all as illustrated in FIG. 24. Opensides 56, 58 of skirt 38 include holes, which have not been numbered inthe figures, via which suitable sheet metal screws or other fastenerssecure open sides 56 and 58 and therefore skirt 38 to adjoiningvertically-oriented walls 60, 62 of a hopper 12. Walls 60, 62 adjoin oneanother at a right angle and are as illustrated in FIG. 15. One suchsheet metal screw, which has been designated 64, is illustrated in FIG.15 securing an open side 56 of skirt 38 to vertical wall 62 of hopper12.

Skirt 38 further includes a closed top portion 66 having an aperture 68formed therein. Piston-cylinder combination 18 is secured in place onclosed top 66 of skirt 38 and passes through aperture 68 with securementbeing effectuated by a nut 70 which threadedly engages a threadedportion of the housing of piston-cylinder combination 18, retaining thepiston-cylinder combination 18 in position on closed top 66 of skirt 38as illustrated in FIGS. 16 and 17.

Skirt 38 is preferably formed by folding a single piece of sheet metalinto the shape of closed sides 52, 54 and open sides 56, 58. Closed top66 is preferably welded onto the single piece of metal folded to formclosed sides 52, 54 and open sides 56, 58 of skirt 38.

Further forming a portion of each valve assembly 19 in each hopper 12 isa valve holder base illustrated in FIGS. 20, 21 and 22 and shown inposition within hopper 12 in FIGS. 15, 16 and 17. The valve holder baseis designated generally 72 and is preferably fabricated from a singlepiece of sheet metal. Valve holder base 72 includes a flat, horizontallydisposed planar portion 74 and a pair of upstanding side walls 76, 78.

Within planar portion 74 is an aperture 80 which is of suitable size forsliding clearance of the lower portion of tubular stem member 40, whichresides within and reciprocates along aperture 80 in planar portion 74as illustrated in FIGS. 16 and 17.

Side walls 76, 78 include holes formed therein to receive sheet metalscrews 64 which retain valve holder base in position at the bottom ofhopper 12 by passage through hopper vertical walls 60, 62. One of sheetmetal screws 64 is illustrated in FIG. 17 retaining valve holder base inposition within hopper 12.

The configuration of valve holder base 72 and the diameter of aperture80 vis-a-vis the outer diameter of tubular stem member 40 are such thatgranular or other material contained within hopper 12 cannot passbetween the exterior of tubular stem member 40 and the periphery ofaperture 80. Additionally, other than aperture 80, valve holder base 72and particularly planar portion 74 thereof close off the bottom ofhopper 40. As a result, for any granular material contained withinhopper 40 to exit downwardly therefrom, that granular material must passthrough the hollow interior of tubular stem member 40.

The two closed sides 52, 54 of skirt 38 have rectangular cutouts formedtherein at the lower extremities thereof. One of these cut-outs formedin the lower portion of closed side 52 is designated 82 in FIG. 23.Since cut-outs 82 are formed in the lower portions of closed sides 52,54 of skirt 38, and since closed sides 52, 54 of skirt 38 are not infacing contact with vertical walls 60, 62 of hopper 12, the twocommunicating rectangular cutouts 82 form an open notch 84 in skirt 38at the lower extremity thereof, facing away from the interior corner ofhopper 12 defined by the juncture of vertical sides 60, 62. Notch 84 isspecifically defined by a pair of vertical edges 86 formed respectivelyin closed walls 52, 54 and a horizontal edge 88 formed in closed walls52, 54, as illustrated in FIGS. 23 and 25.

As shown in FIGS. 26, 27 and 28 tubular stem member 40 also has a notch90 formed therein. Notch 90 is defined by a pair of semi-circular edges92 and a pair of vertically extending edges 94 connecting edges 92thereby to define a semi-cylindrical notch 90.

As illustrated in FIGS. 16 and 17 showing the valve assembly 19 inhopper 12 in the open and closed positions respectively, at the openposition the piston in piston-cylinder combination 18 is extended suchthat piston rod 42 is vertically extended downwardly and notch 90 intubular stem member 40 is in facing communication with notch 84 in skirt38. With tubular stem member 40 in this relationship with skirt 38,communication between notch 84 and notch 90 permits flow of granularmaterial downwardly from within hopper 12 into the hollow interior oftubular stem 40 and downwardly therethrough out of hopper 12. Thisconfiguration is illustrated in FIG. 16.

When the piston in piston-cylinder combination 18 is retracted, tubularstem member 40 is carried upwardly into a position at which notch 90 isnot in communication with notch 84. At this position, communication fromthe interior of hopper 12 with notch 90 is blocked by closed sides 52,54 of skirt 38 as illustrated in FIG. 17. As a result, granular materialwithin hopper 12 cannot reach the hollow interior of tubular stem member40 and thus cannot flow downwardly through the hollow interior oftubular stem member 40 out of hopper 12. Hence, the valve assembly 19 isclosed when in the position illustrated in FIG. 17.

Piston-cylinder combination 18 is preferably a spring-loadedpiston-cylinder combination such that a spring within the cylinderserves always to urge the piston portion of the combination verticallyupwardly considering FIGS. 16 and 17 into the position at which tubularstem member 40 does not communicate with the interior of hopper 12 andhence valve assembly 19 is closed. Application of pneumatic pressure topiston-cylinder combination 18 drives the piston of the combinationdownwardly, against the force of the spring, thereby moving tubular stemmember 40 into the position at which the valve member 19 is open. Thevalve member remains open for so long as the pneumatic pressure isapplied to piston-cylinder combination 18. When the pneumatic pressureis released, the spring forces the piston vertically upwardly in FIGS.16 and 17, thereby closing valve member 19.

An important aspect of the invention is the feature whereby the valvemembers designated generally 19 are entirely contained within hoppers 12and are fixedly secured thereto. As a result, when an operator desiresto change a hopper, all that is required is for the operator todisconnect a pneumatic tube from a pneumatic fitting 96 on a givenhopper and lift the hopper off of the supporting cross-frame 21 andoutwardly flared guide flaps 34 on which the hopper rests. Note thathoppers 12 are not mechanically secured to the remainder of blender 10;this is not necessary. The external pneumatic fitting for each hopper isdesignated 96 and illustrated in FIG. 13. A pneumatic line 98 leads fromfitting 96 to the piston-cylinder combination 18 within each hopper 12;this is illustrated in FIG. 14.

One of the important features of this invention is the compact size ofthe gravimetric blender. The compact size of this blender facilitatesuse of this blender with very small injection molding and compressionmolding machines and with small extruders. The small size of the blenderin the preferred embodiment of the invention facilitates dispensing ofexceedingly small and precisely measured amounts of plastic resinmaterial and other granular materials, as well as liquid color if thatmight be desired as a part of the blend, for supplying such smallmolding machines and extruders.

In the preferred embodiment of the invention, hoppers 12 are eightinches square at the upper extremities thereof; this is denoted bydimension A in FIG. 14. The close spacing together of adjacent hoppers,with adjacent hoppers being only about one-eighth inch apart, which isthe thickness of the cross-members defining cross-frame 21, results inan overall maximum width dimension indicated as B in FIG. 14 of aboutsixteen and one-eighth inches in the preferred embodiment of theinvention.

Similarly, the blender in the preferred embodiment of the invention isvery compact in height. In the preferred embodiment, the blender is onlyabout twenty-two inches from the top of the hoppers to a base portion ofthe blender frame. This twenty-two inch dimension is indicated bydimensional arrow C in FIG. 13. The pneumatic piston which preferablyactuates the weigh bin to dump the weigh bin contents into the mixingchamber is preferably about eleven and five-eighth inches above thebase; this dimension is indicated by dimensional arrow D in FIG. 13.

With this arrangement of hoppers 12 as illustrated generally in FIGS. 13and 14, the blender of the invention may be operated with only a singlehopper in place or with two or with three or all four hoppers in place.Absence of one hopper or more than one hopper does not adversely affectoperation.

Depending on the particular material being fed and blended,piston-cylinder combinations 18 may be operated to open and to closevalve members 19, i.e. to move valve members 19 between open and closedpositions. Alternatively, if it is desired to very precisely regulatethe amount of granular material supplied from a given hopper 12,piston-cylinder combination 18 may be operated in a pulsating fashionwith the piston rapidly reciprocating as pulses of pneumatic pressureare alternately applied and relieved respecting the piston ofpiston-cylinder combination via pneumatic fitting 96.

FIGS. 18 and 19 illustrate an alternate embodiment of the tubular stemmember which has been designated 40A in FIGS. 18 and 19. In thisembodiment, tubular stem member 40A has a blocking wall 100 positionedin notch 90 where blocking wall 100 includes a horizontal portion 102and a vertically extending portion 104. Horizontal portion 102 runsalong and is secured to a lower one of semi-circular edges 92 whilevertical portion 104 extends vertically upwardly therefrom and runsalong and is connected to vertical edges 94 up to approximately thevertical midpoints thereof, as illustrated in FIG. 19. An outwardlyangled lip, of generally curved configuration, designated 106 in FIGS.18 and 19 may be optionally provided at the upper extremity of verticalportion 104; the optional character of outwardly angled lip is denotedby the dotted lines in which it is shown in FIGS. 18 and 19.

With this configuration of the blocking wall 100 in place on tubularstem member 40A, when the associated piston-cylinder combination isoperated in a pulsed fashion, the rate of dispensing of granularmaterial from the associated hopper may be extremely closely controlled.

Referring to FIG. 13 positioned within and preferably slidably retainedby frame 14 below weigh bin 15 is a mix chamber 20 having a mixing meanswhich is preferably in the form of a mixing agitator 22 rotatablydisposed therewithin. Agitator 22 is mounted for rotation about an axis24 preferably shared with a pneumatically powered reciprocating rotarydrive (not shown).

Weight of material in weigh bin 15 is preferably sensed by a load cell32 which is preferably connected to a microprocessor control, notillustrated in the figures, which regulates operation of gravimetricblender 10 through electrical connection with the load cell 32, theactuators which control the piston-cylinder combinations 18 whichactuate the valves 19, the pneumatic drive, the piston-cylindercontrolling weigh bin dump and the like.

The microprocessor provides control of gravimetric blender 10 bymonitoring, preferably on a continuous basis, weight of material, ifany, at a weighing station defined by weigh bin 15. By sensing theweight of material within the weigh bin 15 and actuating appropriatepiston-cylinder combinations 18 in given hoppers 12, the microprocessorserially meters respective components of solid granular resinousmaterial to the weighing station defined by weigh bin 15 until apre-selected weight of each of the respective components has arrived atthe weigh station.

Blender 10 preferably operates by blending components by weight based onsettings provided to and retained within the microprocessor.

Each granular material component is preferably dispensed separately intoweigh bin 15 and then all components are dropped together into mixingchamber 20.

Blender 10 is designed to mount directly over the feed throat of aprocess machine used to mold or extrude plastic material with blender 10being bolted or otherwise fixedly connected to the process machine.

When exclusively solid materials are being blended, typically regrindmaterial is dispensed first according to the percent of regrind materialrequired. If no regrind material or a limited amount of regrind materialis present, then portions of natural material, solid color material andadditive material are increased to bring about a full batch weight.Natural material is typically added second. The amount of naturalmaterial added is preferably calculated by the microprocessor to leaveexactly the right amount of room in the mix chamber for the solid colormaterial and additive material. Once the natural material fill portionof the cycle has been completed, the exact weight of the naturalmaterial that has been actually dispensed is determined to detect anyerrors. Based on this actual weight of natural material dispensed, coloradditive in the form of solid color additive material is metered intothe weigh bin, then other solid additive materials are metered into theweigh bin in the same manner. All components are then dumped into themixing chamber which is preferably continuously running.

In the case where liquid color material is used in place of solid colormaterial, the liquid color material is preferably added to the weigh binlast.

The microprocessor provides the serially metered components and theoptional preselected weight of liquid color material unitarily to amixing station defined by mix chamber 20 by opening weigh bin 15 therebyto permit the materials vertically supported thereby to fall downwardlyinto the mix chamber. Weigh bin 15 is preferably opened by a pneumaticpiston-cylinder combination 136, which is controlled by themicroprocessor and is illustrated in FIG. 13. Pneumatic piston-cylindercombination 136 is mounted on frame 14 and is proximate to, but not incontact with, weigh bin 15 so that weigh bin 15 opens responsively tomovement of the piston member of the piston-cylinder combination 136.

Weigh bin 15 is illustrated in FIG. 13 in solid lines in the closedposition. Weigh bin 15 is opened by actuating piston-cylindercombination 136, causing a piston rod to extend.

When weigh bin 15 is in the closed position, there is no contact norconnection with the piston or its actuating cylinder.

In mix chamber 20 the solid material components which have beenpreferably unitarily supplied and serially metered in weigh bin 15, andoptionally a pre-selected weight of liquid color material, are mixedinto a blend preparatory to being supplied to the manufacturingprocessing machine such as a molding press or an extrusion machine.

Desirably, monitoring of weight of material at the weighing station isperformed continuously by the microprocessor continuously digitallysensing signals supplied by the load cell identified generally 32. Weighbin 15 is suspended by and from load cell 32 with respect to frame 14.

The microprocessor actuates to dispense material as required.

The solenoid valves and especially the solenoid actuators of the valvesare preferably maintained within an enclosed frame which is remote fromthe blender and hence is not shown in the figures. As with themicroprocessor, the valves and their associated actuators are preferablyremote from the gravimetric blender, being connected thereto viasuitable pneumatic tubing.

Vertically extending extremities may provide an open envelope structurewhich permits weigh bin 15 and particularly a weigh bin bracket to moveslidably horizontally, in a direction perpendicular to the plane of thepaper in FIG. 13, to be positioned so that weigh bin 15 effectivelyhangs on and is cantilevered from load cell 32.

Affixed to load cell 32 for receiving the weight load and transferringthe same to load cell 32 is a load transfer beam having an upperhorizontally extending portion fixedly connected by a screw to the uppersurface of load cell 32, a lower generally horizontally extendingportion and a central portion extending between upper and lower portionsand being slightly canted from the vertical. Load cell 32 senses theweight load of weigh bin 15 and any material contained therein by strainresulting at the upper surface of load cell 32 where the load transferbeam is fixedly connected thereto. Load cell 32 is fixed to a load cellenclosure box, particularly to a lower horizontally extending portion ofthe load cell enclosure box via suitable screws.

Affixed to a central portion of a load transfer beam is a load transferplate which is preferably slotted at the central portion thereof withthe slot being relatively short, preferably being only about 1 inch inlength, to receive a screw which extends laterally from vertical portionof a weigh bin bracket, as weigh bin 15 is slidably positioned on andsupported by a load transfer plate. In this position weigh bin 15 may beeffectively cantilevered with respect to load cell 32 and the loadrepresented by the weight of the weigh bin 15 and any material containedtherein is transferred directly to load cell 32 by the load transferplate and load transfer beam, with load cell 32 effectively sensing theweight of material contained within the weigh bin 15.

To protect load cell 32 from contact and possible damage by operators,load cell 32 is preferably within a load cell enclosure box asillustrated in FIG. 13. The load cell enclosure box is in turnpreferably connected to a load cell mounting plate by suitable nut andbolt combinations. The nut and bolt combinations are spaced away fromand do not contact frame 14.

Load cell 32 is fixedly connected to the bottom of the load cellenclosure box via screw connectors which rigidly hold the load cell inposition vis-a-vis the load cell enclosure box. Hence the bottom of theload cell is fixed whereas the upper portion of the load cell, where theload is sensed, is free to deflect in response to loads applied asresult of material being in the weigh bin 15.

Suitable load cells are available from Tedea Huntleigh, an Israelicompany. Model 1010 load cells available from Tedea Huntleigh may beused.

Solenoid actuated valves are available in the United States under thetrademark MAC; the model 45A-L00-DDAA-1BA9 is suitable.

Weigh bin 15 includes a stationary open bottomed basket portion 108illustrated in FIGS. 39 and 40 where basket portion 108 is also visiblein FIG. 13. Basket portion 108 is preferably formed of sheet metal inthe manner shown generally in FIG. 39 with planar front and rearportions designated 110, 112 in FIGS. 39 and 40. The top of basket 108is open to receive granular material, and optionally liquid color, fromabove, with the granular material being supplied from one or more ofhoppers 12.

Basket 108 further includes one vertically elongated side 114 at oneside of basket 108 and a vertically foreshortened side 116 at the otherside of basket 108.

Basket 108 further includes a sloped downwardly facing surface 118. Thebottom of basket 108, designated 121 in FIGS. 39 and 40, is open topermit downward flow of granular and, optionally, liquid color material,out of basket 108.

Weigh bin 15 further includes a dump flap designated generally 120 inthe drawings which is pivotally connected to basket portion 108 so thatupon pivotal motion of dump flap 120, the contents of basket 108 aredropped out of weigh bin 15 and permitted to fall into mix chamber 20.Dump flap 120 is illustrated in FIGS. 37 and 38 and is also clearlyvisible in FIG. 13.

As shown in FIGS. 37 and 38, dump flap 120 includes a pair of upstandingwall portions 122, 124, both of which extend generally verticallyupwardly from a planar bottom portion 126. Dump flap 120 furtherincludes an angled bottom portion 128 which is positioned at an angle toessentially complementally fit against sloped downwardly facing surface118 of basket 108, as shown in FIG. 13.

Upstanding walls 122, 124 of dump flap 120 have apertures 130 formedtherein on a common horizontal axis. Apertures 130 receive pin, screw orother pivotal connection means for pivotally connecting dump flap 120 tobasket 108 through similar apertures 132 formed in sides 110, 112 ofbasket 108.

Affixed to a vertical extremity of an upstanding extension portion ofupstanding wall 124 of dump flap 120 is a flat head rivet 134, which ispreferably welded in position.

Mounted in one of solid side panels 30 of frame 14, specifically theright hand solid side panel 30 as illustrated in FIG. 13, is apiston-cylinder combination designated generally 136 in FIG. 13.Piston-cylinder combination 136 is preferably mounted using a suitablythreaded nut, illustrated in FIG. 13 but not numbered, which engages athreaded collar portion of piston-cylinder combination 136 protrudingthrough an aperture of suitable size in side panel 30.

Affixed to the end of a piston rod extending from piston-cylindercombination 136 is a preferably plastic, such as nylon, knob 138illustrated in FIG. 13.

When material within weigh bin 15 is to be dumped, piston-cylindercombination 136 is actuated by supply of pressured air thereto. Thiscauses the piston portion of piston-cylinder combination 136 to extend,moving to the left in FIG. 13. As a result, knob 138 contacts the flathead rivet 134 which is fixed in the upper extremity of vertical sidewall 124 of dump flap 120 thereby causing dump flap 120 to pivot in acounterclockwise direction, viewed in FIG. 13, about a pivot pointdefined by pivotal connections mounted in apertures 130 illustrated inFIG. 13.

This pivotal, rotary motion of dump flap 120 in a counterclockwisedirection (considering FIG. 13) about pivot point 130 opens the bottomof basket 108 permitting material contained within the weigh bin definedby dump flap 120 and basket 108 to drop into the mixing chamber.

Note that knob 138 only contacts flat head rivet 134 whenpiston-cylinder combination 136 has been actuated and the dumpingoperation is taking place. At all other times, there is no physicalcontact between weigh bin 15 and knob 138. A spring 190 biases dump flap120 towards the closed position.

Weigh bin 15 is connected to load cell 32 through an aperture in solidside panel 30 of frame 14, specifically the left hand one of solid sidepanels 30 considering FIG. 13, by a slide mount bracket 140 which isbolted to load cell 32 and extends laterally and then upwardly to fitwithin a downwardly facing lip 142 formed at an upper extremity ofvertically elongated side 114 of basket 108, as illustrated in FIG. 39.Hence, basket 108 and therefore weigh bin 15 effectively hang from loadcell 32 so that load cell 32 senses the weight of weigh bin 15 and anygranular and, optionally, liquid color, material contained within theweigh bin.

Other suitable means for mounting weigh bin 15 respecting load cell 32are disclosed in pending U.S. patent application Ser. No. 08/763,053,now U.S. Pat. No. 6,007,236, filed in the name of Stephen B. Maguire onDec. 10, 1996, and Patent Cooperation Treaty patent applicationPCT/US96/19485, filed Dec. 10, 1996 by Maguire Products, Inc., thedisclosures of which are incorporated by reference.

Mixing agitator 22 is rotatably journeled in preferably transparent,removable front panel 17 of frame 14. Panel 17 fits closely alongforwardly facing edges of solid side panels 30 and is fixed thereto viaquick release, hand-actuated clips designated generally 144 in FIG. 13.These clips are mountingly connected to a horizontal bar 154 extendingacross front panel 17 at a lower portion thereof, which provides asolid, preferably metal receptacle mounting for journeling of agitator22 in transparent removable front panel 17.

Fixed rotatable journeling of agitator 22 in transparent removable frontpanel 17 provides an important safety feature. If an operator removesfront panel 17 by disengaging clips 144, agitator 22 remains fixed tofront panel 17 and disengages from the rotary reciprocating drive means,discussed below, and is removed from the mix chamber 20 whenever frontpanel 17 is removed from blender 10. This provides an important safetyadvantage in that agitator 22 ceases rotation as panel 17 is moved evenslightly away from contact with solid side panels 30. Hence, if anoperator reaches inside blender 10, there are no moving parts to inflictinjury when front panel 17 has been removed.

As illustrated in FIGS. 33 and 34, agitator 22 includes a central shaftportion 146 with a number of spokes 148 extending radially outwardlytherefrom. Extending longitudinally along the outer extremities ofradial spokes 148 are mixer rails 150 which extend longitudinally alonga major length of central shaft 146 and are curved radially inwardly atthe ends of rails 150 which are remote from front panel 17 when theagitator is journeled in panel 17.

Journeling of central shaft 146 in front panel 17 is accomplished usinga plastic, preferably Nylon or Celcon, cylindrical bearing member 152illustrated in FIG. 13. The left end of shaft 146 (when considering FIG.34) fits into bearing member 152. Mixer rails 150 and particularly thecurved, radially inwardly facing extremities thereof 151 stop short ofcenter shaft 146 in order to provide clearance for a coupling memberwhich removably connects the agitator 22 to the rotary reciprocatingdrive means.

To facilitate removal of front panel 17 from blender 10, and to providestrength for journeling of-bearing member 152 in front panel 17, thehorizontal metal bar or strap 154 is affixed to front panel 17 andprovides a position of attachment for clips 144. A handle 156 is mountedon strap 154 and provides convenient hand gripping for removal of frontpanel 17 when clips 144 have been disengaged.

Agitator 22 is driven in a manner to reciprocatingly rotate so thatagitator 22 rotates about axis 24 defined by central shaft 146 throughan angle of about 270° and then reverses, rotating in the oppositedirection thorough an angle of about 270°. This is accomplished by usinga drive consisting of two pneumatically driven piston-cylindercombinations reciprocating a rack to which a pinion gear is connected.This drive means is a purchased item and is mounted on the exterior of arear panel 30 of frame 14 in position to provide coaxial drivingrotation of agitator 22.

Means for coupling and decoupling agitator 22 to the reciprocatingrotational drive means is provided by a coupling assembly having maleand female members which are illustrated generally in FIGS. 29 through32.

The smaller of the two members forming the coupling is designatedgenerally 158 and is illustrated in FIGS. 31 and 32. This smaller memberis referred to as a male member and is generally cylindricallyconfigured with a curved, cylindrical exterior surface 160, an axiallyelongated bore 162 extending therethrough and a transverse bore 164.Axially elongated bore 162 is of appropriate size for fitting of malemember 158 on end 146R of shaft 146 of agitator 22, as illustrated inFIG. 34. Set screws or suitable pins in transverse bore 164 may be usedto affix male member 158 to end 146R of central shaft 146.

Formed in outer surface 160 of male member 158 are a plurality ofangularly evenly spaced flutes 166 which extend axially respecting malemember 158 and are concave, as illustrated in FIG. 32. Concave flutes166 are provided to receive and to fit about pins which extend outwardlyfrom a female member 170 as illustrated in FIGS. 29 and especially inFIG. 30, with one pin 172 being illustrated in position in FIG. 30. Thelongitudinal extremity of male member 158, which faces away fromagitator 22 and towards female member 170 when male member 158 isassembled on and affixed shaft 146, is chamfered with such chamfersindicated as 168 in FIG. 31. These chamfers facilitate engagement ofmale member 158 generally and specifically of flutes 166 with pinmembers 172 of female member 170, so that the pin members may residewithin flutes 166 in essentially complemental, facing contact. Malemember 158 is preferably plastic, most preferably Celcon or Nylon.

Female member 170 illustrated in FIGS. 29 and 30 is of generallycylindrical configuration, with an annular shoulder 174 defining astepdown from a larger cylindrical diameter to a smaller cylindricaldiameter. The end of female member 170 of smaller cylindrical diameteris the end which is closer to the source of reciprocating rotationalmovement and is journaled in a rear solid panel 30 of frame 14, in aposition of axial alignment with bearing member 152 when transparentremovable front panel 17 is in position as a part of frame 14.

Female member 170 further includes a longitudinal bore 176 extending thelongitudinal length thereof with a keyway 178 formed in bore 176. Keyway178 is provided for fitting about a driving shaft providing the sourceof reciprocating rotational movement for agitator 22.

A pair of radial bores 180 are provided in the larger cylindricalsectional portion of female member 170 for set screws or other pinconnections to tightly retain female member 170 on the drive shaftcoming from the source of reciprocating rotational motion.

As can readily be envisioned by comparing FIGS. 30 and 32, pins 172 fitwithin flutes 166 and easily find those flutes 166 when the front panel17 is put into position and the male member 158 fixedly connected toshaft 146 is pushed towards female member 170 and especially pins 172.Chamfer surfaces 168 on male member 158 facilitate pins 172 findingflutes 166 and moving into complemental, facing engagement therewith.Once this has been accomplished, driving rotation of female member 170by the reciprocating rotational drive means results in correspondingone-to-one rotation of male member 158 and consequent rotation ofagitator 22.

One of the important features of the invention is that the integralconstruction of the valve and hopper assembly permits the valve to beremovable integrally with the hopper, thereby permitting various sizevalves to be mounted in hoppers. This facilitates changing of valve sizeby the user so that the user merely need remove the hopper having agiven size valve and substitute another hopper having a smaller or otherdesired size valve in its place. The integral valve-hopper design alsocontributes to safety in that individuals cannot actuate a valve andinjure themselves when a hopper is removed from the blender. The valveand the shut-off mechanism for granular material simply is not presentwhen the hopper is not in place. Once the hopper is in position, anindividual cannot insert the individual's fingers into the way of any ofthe moving parts of the valve within the hopper.

The air cylinders actuating the valves are preferably spring return aircylinders; internal springs act to pull the cylinder pistons up and pullthe rods attached to the pistons into the vertical position, creating ashut-off. When the tubular members 40 are in the extreme verticallyupward positions, no material can flow downwardly therethrough; thehopper is necessarily closed at the bottom and can easily be removedwithout spilling any material that may be in the hopper.

In the variation of this valve which is illustrated in FIGS. 18 and 19,where the hemispheric or half-circular opening in a tubular portion iscovered at the bottom and has a wall running upwardly, this tubularvalve member 40A may be reciprocated up and down to provide veryaccurate downward metering of material. When such accurate metering ofmaterial is desired, a stroke limiter in the form of a sleeve of plasticmay be used on the rod 42 which connects the associated piston to theyoke 44.

The piston-cylinder combination 18 is desirably reciprocatedelectronically, permitting the piston to cycle up to six times persecond providing the reciprocation of the tubular stem member 40A. Skirt38 is stationary, fitting around the reciprocating tubular stem member40A, skirt 38 is secured to hopper 12 by sheet metal screws goingthrough the hopper into the skirt. The skirt is stationary when thevalve is in the hopper and shields the tubular stem member 40 as tubularstem member 40 moves up and down. Skirt 38 allows granular material toenter tubular stem member 40 only when tubular stem member 40 andparticularly the notch 90 therein is below the horizontal edge 88defining the upper boundary of notch 84.

Skirt 38 is preferably a single piece of sheet metal having twofull-size or closed sides and two shortened or flanged or open sidesfacing the two surfaces or walls of hopper 12 to provide completeclosure around tubular stem member 40.

One pneumatic line preferably goes to each hopper 12 with a quickdisconnect fitting to allow the hopper to be removed from the blender.Air is pulsed back and forth by solenoid valves. Since thepiston-cylinder combinations have spring return pistons, only one lineis needed to each piston-cylinder combination. This is in contrast toprior art gravimetric blenders in which two lines are provided topiston-cylinder combinations driving the various slide gates and otherparts of the machine.

In the instant invention, the pneumatic supply line goes through theside of each hopper 12 and connects to the piston-cylinder combinationwithin the hopper. Removal of the hopper and piston-cylinder combinationis facilitated by disconnecting the pneumatic line at the quickdisconnect fitting 96 provided on the exterior of each hopper 12 andpicking off each hopper 12 and its associated piston-cylinder assembly18 which is one effectively unitary assembly and may be lifted directlyoff of the top of blender 10.

Another important aspect of the invention is in the provision of theseparation of knob 138 from flat head rivet 134 for opening the dumpflap 120 of weigh bin 15. With piston-cylinder combination 136 and knob138 physically separated from weigh bin 15, there is no externalconnection to weigh bin 15 during the weighing process and therefore,there is no chance of something such as a pneumatic line introducing anerror into the weighing procedure.

Respecting mixing chamber 20, mixing chamber 20 is equipped with acurved side and bottom member which slides into and, out of the mixingchamber. This curved member is visible in FIG. 13, is illustratedseparately in FIGS. 35 and 36 and is designated generally 182 in thefigures and sometimes referred to as a mix chamber insert slide. Insertslide 182 rests on a plastic saddle 184 which is visible in FIG. 13.Saddle 184 is secured to the metal bottom 186 of frame 14. Solid sidepanels 30 of frame 14 are preferably welded to bottom 186 along thethree sides of respective contact therewith. Bottom 186 preferablyprotrudes forwardly relative to sides 30 so as to provide a bottomsupport transom for transparent removable front panel 17 when panel 17is in place on blender 10.

The reciprocating rotational motion provided by the drive unit rotatesagitator 22 approximately 270° in one direction and then 270° in theopposite direction.

One advantage of the coupling defined by male and female members 158,170 with the pins 172 of female member 170 engaging the flutes 166 ofmale member 158 is that there are no closed bottom holes into which pins172 must fit. With an “open” coupling such as provided by male andfemale members 158, 170, there is less likelihood of catching pellets ofthe granular material in the coupling itself.

Yet another feature of the invention is with agitator 22 being journaledwithin and removable unitarily with transparent removable front panel17, there is no need for any interlock between front panel 17 and thedrive means providing the reciprocating rotational drive for theagitator. Since agitator 22 is removed with transparent front panel 17,whenever panel 17 is removed, the only moving part remaining in themixing chamber is the rotating female member 170.

When the blender of the invention is used, there is preferably a singlecontroller provided for each blender at a remote locale. The controllerand microprocessor preferably are not mounted on the frame of theblender as is the case with known, larger gravimetric blenders.

Material components which should be fed and controlled in very, verysmall amounts, such as color components, may be controlled to levels of3% or 4% of the total blend when the pulsing action of a piston-cylindercombination is applied to a modified version of the tubular stem member40A as illustrated in FIGS. 18 and 19. In addition to color additives,ultraviolet stabilizers, inhibitors, strengtheners and the like sometimeneed to be fed in such very, very small amounts into plastic resinblends prior to molding.

In the blender, there is provided a proximity sensor, which is notindicated in the figures. This sensor fits through a rear wall 30 offrame 14 and protects the machine by shutting off the machine whenmaterial in the mix chamber reaches a certain level. These proximitysensors are known in the art.

Using the modification of the tubular stem member 40A illustrated inFIGS. 18 and 19 and with pulsing action of the spring equippedpiston-cylinder combination 18 allows very fine feeding of material. Ifair pressure is reduced to piston-cylinder combination 18, so as tosoften the severity of the reciprocation of the air cylinder, the aircylinder can be regulated to a point where as little as two to threegrams of material per second can be accurately fed and feeding can berepeatedly controlled at that rate.

Utilizing the reduced size gravimetric blender of the invention,approximately 400 grams of material may be produced in less than oneminute. Hence, about fifty pounds per hour of blended resin material canbe produced using the blender of the invention.

The valve assembly 19 with the full half-cylindrical notch go in thetubular stem member as illustrated in FIGS. 26 and 27 may dispensematerial at about 35 grams per second. When the pulsing technique isused, and the modified version of the tubular stem member 40Aillustrated in FIGS. 18 and 19 is used, feeding of plastic resinmaterial pellets can be controlled to less than one gram per second.

I claim the following:
 1. A gravimetric blender comprising: a. avertically elongated rectangular frame having at least one of atransparent panel or open side between panels extending substantiallythe vertical height of said frame; b. a material storage hopperremovably mounted on said frame and comprising means within said hopperand proximate the hopper bottom for dispensing material within saidhopper; c. a weigh bin connected to said frame below said hopper; d.means connected to said frame for sensing weight of material in saidbin; and e. a mix chamber below said weigh bin.
 2. The gravimetricblender of claim 1 wherein said means for dispensing material withinsaid hopper includes a valve and means for actuating said valve, whereinsaid valve and said valve actuating means are fixedly connected to saidhopper.
 3. The blender of claim 2 wherein said actuating means is atleast partially within said hopper.
 4. The blender of claim 3 whereinsaid valve means is at least partially within said hopper.
 5. Theblender of claim 3 wherein said valve means is fully within said hopper.6. The blender of claim 2 wherein said actuating means is fully withinsaid hopper.
 7. The blender of claim 2 wherein said hopper with saidvalve and actuating means affixed thereto is manually removable fromsaid frame.
 8. The blender of claim 2 further comprising a plurality ofhoppers, each with valve means therewithin and respective individualvalve actuation means.
 9. The blender of claim 2 wherein said actuatingmeans is pneumatically driven and includes a vertically elongated memberfor transmitting motion to said valve.
 10. The blender of claim 2wherein said actuating means comprises a piston-cylinder combinationconnected to said hopper wall.
 11. The blender of claim 1 furthercomprising means connected to said frame for selectably contacting andopening said bin to release material in said bin downwardly into saidmix chamber.
 12. The blender of claim 11 wherein said means forselectably contacting and opening said bin is pneumatically actuated.13. The blender of claim 11 wherein said means for selectably contactingand opening said bin is a piston-cylinder combination.
 14. The blenderof claim 13 wherein said cylinder is outward of said frame.
 15. Theblender of claim 13 wherein said piston moves transversely to the axisabout which said openable portion pivots.
 16. The blender of claim 13wherein said piston contacts said bin directly.
 17. The blender of claim13 wherein said piston contacts said bin indirectly.
 18. The blender ofclaim 1 further comprising means for biasing an openable portion of saidbin towards a closed position.
 19. The blender of claim 18 wherein saidopenable portion is movable about a pivot.
 20. The blender of claim 19wherein said openable portion pivots about a horizontal axis.
 21. Theblender of claim 18 wherein said openable portion is pivotally connectedto a remaining, stationary portion of said bin.
 22. The blender of claim1 wherein said frame is a single piece of material.
 23. The blender ofclaim 22 wherein said frame is steel.
 24. The blender of claim 22wherein said frame has three closed sides, two of which are parallel andperpendicular to the remaining closed side.
 25. The blender of claim 22wherein said frame extends vertically upwardly in a straight line fromthe bottom of said blender to said hopper.
 26. The blender of claim 22wherein one side of said frame is open.
 27. The blender of claim 22further comprising an upwardly extending removable panel adapted forfitting together with said frame to provide an enclosure for said weighbin.
 28. A gravimetric blender comprising: a. a frame; b. a weigh binmounted on said frame, having an aperture at the bottom thereof andcomprising; i. a movable weigh pan defining a portion of the bin bottom,being moveable between positions at which a portion of said pan coverssaid aperture and at which said aperture is open; ii. a sloped sectionforming a portion of said bin bottom and extending downwardly from a binside; iii. remaining sides of said bin having co-planar lowerextremities; iv. at least a central part of said pan when said pan is ina position at which said aperture is open being below said slopedportion; c. means, connected to said frame, for sensing weight ofmaterial in said bin; d. a mix chamber below said bin and connected tosaid frame including mixing means therewithin; e. means for selectablymoving said pan between said position covering said aperture at whichsaid pan defines a portion of said bin bottom and said position at whichsaid aperture is open for releasing material in said bin downwardly intosaid mix chamber.
 29. The blender of claim 28 wherein said slopedsection is planar.
 30. The blender of claim 28 wherein said remainingsides of said bin are of common vertical height.
 31. The blender ofclaim 28 wherein said central part of said weigh bin in said apertureuncovering position is parallel with said sloped section.
 32. Theblender of claim 28 wherein said central part of said weigh bin and saidaperture open position is under said sloped section.
 33. A gravimetricblender comprising: a. a vertically elongated frame having a pluralityof vertically elongated panels, two of said panels being spaced apart todefine an open side of said frame therebetween with said panels definingan enclosure for a weigh bin and a mix chamber; b. a material storagehopper mounted on said frame; c. said weigh bin connected to said framebelow said hopper; d. means, connected to said frame, for sensing weightof material in said bin as received from said hopper; e. said mixchamber below said bin and receiving material therefrom includingrotatable mixing means comprising a mixer therewithin; f. an additionalvertically elongated panel adapted for fitting over said open side ofsaid frame to close said enclosure, said additional panel beingtransparent; g. drive means supplying rotary motion for said mixer; andh. means transferring rotary motion from said drive means to said mixerdisconnecting said mixer from said drive means upon disconnection ofsaid additional panel from said frame.
 34. The blender of claim 33further comprising means connecting said mixer to said additional panelfor axial movement of said shaft responsive to said panel disconnectingfrom said frame which provides movement of said mixer unitarily withsaid panel upon panel disconnection.
 35. The blender of claim 33 whereinsaid mixer rotary motion is around an axis perpendicular to saidadditional panel.
 36. The blender of claim 33 wherein said drive meansis operable for supplying arcuate rotary motion to said mixer.
 37. Theblender of claim 36 wherein said arcuate rotary motion supplied by saiddrive means is fixed in amount.
 38. The blender of claim 36 wherein saiddrive means arcuately reciprocates said mixing means.
 39. The blender ofclaim 36 wherein said arcuate motion is less than a full circle.
 40. Theblender of claim 36 wherein said arcuate motion is greater than a fullcircle.
 41. The blender of claim 36 wherein said drive means arcuatelyreciprocates said mixing means through arcs which are less than fullcircles.
 42. The blender of claim 36 wherein said drive means ispneumatically driven.
 43. In a gravimetric blender including avertically elongated frame, at least one granular material storagehopper connected to the frame, a valve for dispensing granular materialfrom the hopper through an orifice in the bottom of the hopper, a weighbin below the hopper to receive granular material dispensed from thehopper, means for sensing weight of granular material received in theweigh bin and a mix chamber below the weigh bin for collecting andmixing granular material dropped from the weigh bin after materialweight has been sensed, the improvement comprising the frame being asingle sheet of metal bent in two places at ninety degree angles alongvertical lines to form three (3) vertically extending panel members,outer ones of the panel members being parallel and extending in a commondirection from the central one of the panel members to define threesides of a rectangle with a fourth side remaining open to expose spacewithin the frame for view of the weigh bin and the mix chamber residingwithin that space, and a transparent panel closing the open fourthrectangular side of the frame and being removably mounted on the frameto permit operator access to the weigh bin and mix chamber residingwithin the frame.
 44. A gravimetric blender including a verticallyelongated frame, at least one granular material storage hopper at thetop of the frame, means for dispensing granular material downwardly fromthe hopper through an orifice in the hopper bottom, a weigh bin belowthe hopper receiving granular material dispensed from the hopper, meansfor sensing weight of granular material received in the weigh bin and amix chamber below the weigh bin for collecting and mixing granularmaterial dropped from the weigh bin after material weight has beensensed, the improvement comprising the hopper resting on supportingstructure forming the top of the frame with the hopper being manuallyremovable by it being liftable from the frame without the use of tools,with the means for dispensing granular material from the hopper throughan orifice in the hopper bottom being fixedly connected to the hopperand removable therewith upon the hopper being lifted from the frame. 45.A gravimetric blender including a vertically elongated frame, at leastone granular material storage hopper connected to the frame, means fordispensing granular material from the hopper through an orifice in thehopper bottom, a weigh bin below the hopper receiving granular materialdispensed from the hopper, means for sensing weight of granular materialreceived in the weigh bin and a mix chamber below the weigh bin forcollecting and mixing granular material dropped from the weigh bin aftermaterial weight has been sensed, the improvement comprising the meansfor sensing weight of granular material received in the weigh bin beinga single means and being mounted outside of the frame on a verticallyextending panel forming one side of the frame and extending the verticalheight of the frame, the weight sensing means having a bracketprojecting into space within the frame through an aperture in thevertically extending panel, the bracket supporting the weigh bin incantilever fashion in the space within the frame, with the weigh binbeing slidably horizontally moveable on the support bracket within theframe for removal from space within the frame.
 46. A gravimetric blenderincluding a vertically elongated frame, a plurality of granular materialstorage hoppers connected to the frame, valves for dispensing materialfrom respective hoppers through orifices in the hopper bottoms, a weighbin below the hoppers to receive granular material dispensed from thehoppers, a load cell for sensing weight of granular material received inthe weigh bin and a mix chamber below the weigh bin for collecting andmixing granular material dropped from the bin after material weight hasbeen sensed, the improvement comprising the frame being a single sheetof metal bent at ninety degree angles along two vertical lines to formthree (3) vertically extending panel members, outer ones of the panelmembers being parallel and extending in a common direction from thecentral one of the panel members to define three sides of a rectanglewith a fourth side remaining open to expose space within the frame forview of and access to the weigh bin and the mix chamber residing withinthat space, a transparent panel closing the open fourth rectangular sideof the frame and being removably mounted on the frame to permit operatoraccess to the weigh bin and mix chamber residing within the frame, thehoppers resting on supporting structure forming the top of the framewith the hoppers being manually removable by their being liftable fromthe frame without the use of tools, with the valves for dispensinggranular material from the hoppers through openings in the bottoms ofhoppers being fixedly connected to hoppers and removable therewith uponthe associated hopper being lifted from the frame, the load cell forsensing weight of granular material received in the weigh bin being asingle load cell mounted outside of the frame on the verticallyextending panel forming one side of the frame and extending the verticalweight of the frame, the load cell having a bracket projecting intospace within the frame through an aperture in the vertically extendingpanel, the bracket supporting a weigh bin in cantilever fashion in thespace within the frame, with the weigh bin being slidably horizontallymoveable on the support bracket within the frame for removal from thespace within the frame.
 47. In a gravimetric blender including a frame,at least one granular material storage hopper connected to said frame,means for dispensing granular material from said hopper through anorifice in the hopper bottom, a weigh bin having an aperture at thebottom thereof and being positioned below said hopper for receivinggranular material dispensed from said hopper, said weigh bin having adump flap pivotally movable between positions at which the dump flapcovers said weigh bin bottom aperture and at which the aperture is open,means for sensing weight of granular material in said weigh bin, and apneumatic piston-cylinder combination for opening said weigh bin afterweight of granular material therein has been sensed for downwarddischarge of granular material therefrom to a mix chamber below saidweigh bin for mixing granular material received from said weigh bin, theimprovement comprising: said means for sensing weight of granularmaterial received in said weigh bin being a single load cell mounted onthe outside of said frame on a vertically extending panel forming oneside of said frame and extending the vertical height of said frame, saidload cell having a bracket projecting through an aperture in thevertically extending panel into space within said frame, said load cellbeing separated from said weigh bin and said mix chamber by the panelforming a portion of said frame, said panel being imperforate other thanfor the aperture through which said bracket extends, said bracketconnecting said load cell and weigh bin, said bracket supporting saidweigh bin in cantilever fashion in space within said frame with saidweigh bin being slidably horizontally moveable on said bracket withinsaid frame for removal from space within said frame, means for biasingthe dump flap towards the position at which the dump flap covers saidweigh bin bottom aperture, the pneumatic piston-cylinder combination foropening said weigh bin selectably contacting and moving said dump flapfrom the position covering the aperture to the position at which theaperture is open to release granular material in said weigh bindownwardly into said mix chamber and being spaced from said dump flapand weigh bin whenever the piston-cylinder combination is de-energizedand said dump flap covers the aperture in the bottom of said weigh binin response to force of a bias spring.
 48. A gravimetric blendercomprising: a. a frame having a vertically extending transparent side;b. a material storage hopper removably mounted on said frame andcomprising means within said hopper for selectably downwardly dispensingmaterial from said hopper; c. a weigh bin, positioned inboard of saidtransparent side and enclosed by said frame below said hopper; d. meansconnected to said frame for supporting said bin and sensing weight ofsaid bin and material therein; and e. a mix chamber below said weigh binincluding a material mixing agitator therewithin rotatable about ahorizontal axis.
 49. A gravimetric blender comprising: a. a frame havingthree sides of unitary construction and a transparent side extending thevertical height of said frame; b. a material storage hopper removablymounted on said frame and comprising valve means within said hopper forselectably downwardly dispensing material from said hopper; c. a weighbin, positioned inboard of and spaced from said transparent sidesupported by said frame below said hopper; d. means connected to saidframe for sensing weight of said bin and material therein; e. a mixchamber below said weight bin and f. mixing means within said chambermovable angularly about an axis perpendicular to said transparent side.50. A gravimetric blender comprising: a. a housing; b. a weigh binmounted on said housing, having an aperture at the bottom thereof andcomprising; i. a movable weigh pan defining a portion of the bin bottom;ii. a sloped section forming a portion of said bin bottom and extendingdownwardly from a bin side; iii. remaining sides of said bin havingco-planar lower extremities; iv. at least a central part of said panwhen said aperture is open being below said sloped portion; c. means,connected to said housing, for sensing weight of material in said bin;d. a mix chamber below said bin and connected to said housing includingmixing means therewithin; e. means for selectably moving said panbetween a position covering said aperture at which said pan defines aportion of said bin bottom and an position at which said aperture isopen for releasing material in said bin downwardly into said mixchamber.
 51. A gravimetric blender comprising: a. a vertically elongatedframe having an open side and defining an enclosure for a weigh bin anda mix chamber; b. a material storage hopper mounted on said frame; c.said weigh bin connected to said frame below said hopper; d. means,connected to said frame, for sensing weight of material in said bin asreceived from said hopper; e. said mix chamber including rotatablemixing means therewithin being located below said bin and receivingmaterial therefrom; f. a vertically elongated panel adapted for fittingtogether with said frame to close said enclosure, said panel beingtransparent; g. drive means supplying rotary motion for said mixer; andh. means for transferring rotary motion from said drive means to saidmixer and operably disconnecting said mixer from said drive means upondisconnection of said panel from said frame.